Thanks Shefali for responding the post.
Referring to the question you raised, i use adobe application only for pdf reading and editing. And also not accessing pdf files via hyperlink/email or from such other entities.
One thing might help you, my previous observation, that copy is created when i exit pdf was wrong..sorry for that.
Copy is created in adobe folder of my internal memory with original name (lets say "abc.pdf") as soon as i open up the pdf and it doesnt get deleted by itself when i exit pdf.
Next time, when i open up the abc.pdf (from original location), copy again is created but with new name, i.e. abc-1.pdf
Hence, whenever I edit pdfs, changes are not saved in original file but only in temporary copies. And i would like to do away of such copies so that i can easily track my changes in original file.
Thanks
Anshul